Object Database system

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SUSHIL KULKARNI

OBJECT DATABASE SYSTEM


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Object Database System :

Objectives

x Problems with RDBMS

x What is ODBMS and ORDBMS ?

x Advantages and Disadvantages

x OO/ER model comparison and object

schema

x Object type : Attributes and Methods

x Collection types


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PROBLEMS


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ProblemsProblems

x Poor representation of real world Entities.

- Relations are too dry, contains only state of a

relation.

- Relationships are not known.

x Example:


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Problems !Problems !

killed

d_no

dok

p_no

treats

d_no

since

p_no

doctor

d_no

telno city

dname

paddress

patient

p

_no

pname


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PROBLEMS !PROBLEMS !

x Homogeneous data structure

All rows have the same number of attributes.

All values in a column are of the same type. All attribute values are atomic.

x

Fixed length of data type, Limited data types Can not store images, audio and video clips.

Spatial, temporal data can not be added.


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PROBLEMS !PROBLEMS !

x Reusability (inheritance) of a table is not possible.

Options are:Object-oriented databases ?

Object-relational databases ?


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Storing Objects in a Relational Database

For the purposes of discussion, consider the inheritance

hierarchy which has a super class:

Staff

and three subclasses:

Manager,

SalesPersonnel,

Secretary.

Begin with ExampleBegin with Example!!


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Map each class to a relation:

Staff(staffNo, fName, IName, position, sex, DOB, salary)



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Map each subclass to a class and convert to relation

Manager (staffNo, fName, IName, position, sex, DOB, salary,

bonus, mgrStartDate)

SalesPersonnel (staffNo, fName, IName, position, sex, DOB, salary,

salesArea, carAllowance)

Secretary (staffNo, fName, IName, position, sex, DOB, salary,

typingSpeed)



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Map the hierarchy to a single relation

Staff(staffNo, fName, IName, position, sex, DOB, salary, bonus,

mgrStartDate, sales-Area, carAllowance, typingSpeed, typeFlag)



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x The best solution of all above problems is in

Object Relational Database Management System.

x For example: In Oracle ,we can create an object Staffin database and then we can create three differenttables namely Manager, Salepersonnel and Secretary,

each refer to object created Staff as one of itsattribute.

x The whole process of designing the above databasewith syntax of Oracle 9i is explained here below:

ORDBMS ApproachORDBMS Approach


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Creation of an object staff:

CREATE TYPE staff AS OBJECT(

staffno number(4) primary key,fname varchar(20),

lname varchar(20),

position varchar(10),

sex varchar(1),

DOB date,

salary number(8,2));

ExampleExample


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The object staff can be referenced in table Manager as one

of its attribute as shown below:

CREATE TABLE manager(staff_detail staff,

bonus number(5),

mgrstartdate date);

ExampleExample


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Let us insert the values:

INSERT INTO manager VALUES

(staff(100,ajay,arora,production

manager,m,25-feb 1976,15000 ),

2000,12-dec-2002);

ExampleExample


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Similarly we create other tables as shown below:

CREATE TABLE salepersonnel(

staff_detail staff,salearea varchar(25),

carallowance number(7));

CREATE TABLE secretary(

staff_detail staff,

typingspeed number(3));

ExampleExample


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In response to the increasing complexity of

database applications, two 'new' data models have

emerged:

Object-Oriented Data Model (OODM)

Object-Relational Data Model (ORDM)

New data ModelsNew data Models


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OO AND ER MODELOO AND ER MODEL

COMPARISIONCOMPARISION

N / AMethod

N / AOID

Primary KeyN / A

AttributesInstance Variable

Entity setClassEntityObject

Entity definitionType

E- R MODELE- R MODELOO DATA MODELOO DATA MODEL


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OODBMSDBMS

ODBMSODBMS

Object Oriented

Features

Conventional DBMSConventional DBMS

FeaturesFeatures

++

OO Concepts

OO Data model

OOPL

Data accessibility

Persistence

Back up & recovery

Transaction

Concurrency

Security


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OODBMSDBMS

ODBMS is the MS process methods applied forDB data structure, which is complied with O

objects.

ODBMS = O * DB * MS


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x Integrating database capabilities with objectprogramming language capabilities, the result is anobject-oriented database management system orODBMS.

x An ODBMS makes database objects appear asprogramming language objects in one or more existingprogramming languages.

x Object database management systems extend the objectprogramming language with transparently persistentdata, concurrency control, data recovery, associativequeries, and other database capabilities.

ODBMSODBMS


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Following is the one of the approach for designing an

object-oriented database:

x The user will create classes, objects, inheritance and

so on.x Database system will store and manage these objects

and classes.

x

Translation layer is required to map the objectscreated by user into objects of the database system.

Object Database (ODBMS) for Java, written entirely in Java, and

compliant with the Java Data Objects (JDO) standard developed

ODBMSODBMS


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x The object-oriented data model allows the 'real world' to bemodeled more closely.

x ODBMSs allow new data types to be built from existing types.

x More expressive query language then SQL.

x Applicability to advanced database applications

There are many areas where traditional DBMSs have not been

particularly successful, such as, Computer-Aided Design (CAD),

CASE, Office Information Systems (OIS), and Multimedia

Systems. The enriched modeling capabilities of OODBMSs have

made them suitable for these applications.

AdvantagesAdvantages


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x No universally agreed data model for an ODBMS, andmost models lack a theoretical foundation.

x In comparison to RDBMSs, the use of ODBMS is stillrelatively limited.

xThere is no standard object-oriented query language.`

x

Lack of support for views.xNo adequate security mechanisms for accessing objects.

DisadvantagesDisadvantages


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ORORDBMSDBMS

ORDBMS is the MS process methods applied for DB

data structure, which is complied with O object and R

Relational concepts.

ORDBMS = ODBMS + RDBMSORDBMS = ODBMS + RDBMS

= (O + R) * DB * MS.= (O + R) * DB * MS.


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This system simply puts an object oriented front end on a

relational database (RDBMS). When applications interface

to this type of database, it will normally interface asthough the data is stored as objects.

The system will convert the object information into data

tables with rows and columns and handle the data the

same as a relational database.

ORDBMSORDBMS


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x The object type can be reuse and share in different application.

x

ORDBMS provides increased productivity both for thedeveloper and for the end user.

x It is just an extension of existing relational approach.

AdvantagesAdvantages


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x Complexity increases and associated costs.

x Simplicity and purity of the relational model are lost.

x Because the ORDBMS converts data between an object orientedformat and RDBMS format, speed performance of the databaseis degraded substantially. This is due to the additional conversionwork the database must do.

DisadvantagesDisadvantages


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OBJECT


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ObjectObject

x Uniquely identifiable entity that contains both the

attributes that describe the state of a real-world

entity and the actions associated with it.

Definition is similar to definition of an entity,

however, object encapsulates both state and

behavior; an entity only models state.

Object Attribute


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Object Attribute

( Instance Variables)

Attributes - contains current state of an object.

- Known as instance variables in OO environment.


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Object State

x Set of values that objects attributes have at a

given time.

x Can vary, although its OID remains the same.

x To change the objects state, change the values

of the objects attributes.


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Object : PERSON

State: Attribute ValueAttribute Name

[email protected]

9967770658Cell no.

24145643Home Tel no.

12/5/1959DOB

SuhasFirst name

AjayMiddle name

DixitLast name

E12345PAN

These are the simple or primitive attributes


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OBJECT SCHEMA: GRAPHICALOBJECT SCHEMA: GRAPHICAL

REPRESENTATIONREPRESENTATION

NAME s

ADDRESS s

DOB s

SEX sAGE i

EMPLOYEE

Sameer A. Sathe

112, L.N.Street ..

23-NOV-1970

M30

SHARED REPRESENTATION FOR ALL OBJECTS OF THE

CLASS EMPLOYEE

INSTANCE VARIABLES OBJECT INSTANCES


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Methods

x Code that performs a specific operation on objects

data.

x Used to change the objects attribute values or to

return the value of selected object attributes.

x Represent real-world actions.


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Depiction of an Object


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DATA TYPES

FORATTRIBUTES


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Data types for attributes

Two types of attributes: Simple & Abstract

x

Simple attribute are conventional attributes likenumber, string ,which takes on literal values.

x They are also called primitive attributes.


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Object : PERSON ( contd)

Attribute ValueAttribute Name

HR, AccountsDept *

Street Address, House Number, City, State

Pin

Address *

*Represents an attribute represent one or more attributes.

Let us consider few attributes for Person object:Let us consider few attributes for Person object:


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Abstract Data Type

xTo add address information for a person , we have to

consider separate attributes: Street Address, House

Number, City , State and Pin using primitive data

types.

xWith abstract data typing, we can create a new data

type and manipulate the data as if it were primitive

data type.


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Operations on ADT

xDBMS allows to store and retrieve images using

CLOB and BLOB like an object of any other type

such as number.

xOne can define operations on an image data type such

as compress, rotate, shrink and crop.

xADT is the combination of an atomic data type and

its associated methods.


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STRUCTURED TYPE

USING ORACLE


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Create EMP Table

x Creating Table with ADT Object Datatype

Now we will create EMP table for employees.

CREATE TABLE EMP( EMPID Number primary key,

EMPLOYEE PERSON);

Table created.


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EMP Structure

xUse DESC command to see the table structure.

SQL> DESC EMPName Null? Type

----------------------- -------- ------------

EMPID NOT NULL NUMBER

EMPLOYEE PERSON


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Insert into EMP

x We will now populate our table.

SQL> INSERT INTO EMP(empid, employee)

VALUES(1001,

person(122,'Sushil','Trymbak','Kulkarni',

'29-jun- 1984','24144386',10000));1 row created.

SQL> INSERT INTO EMP1 (empid, employee)

VALUES(1002,

person(124,'Suhas','Ramchandra','Dixit',

'13-may-1988','24124886',120000));1 row created.


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Select statement on EMP

We can select the records with simple SQL statement. E.g.

SELECT *

FROM EMP

/

EMPID

----------EMPLOYEE(PIN, FIRST_NAME, MIDDLE_NAME, LAST_NAME, DOB,

TEL_NO, SALARY)

-------------------------------------------------------

1001

person(122,'Sushil','Trymbak','Kulkarni','29-jun- 1984','24144386',10000)

1002

person(124,'Suhas','Ramchandra','Dixit',

'13-may-1988','24124886',120000)


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Object IdentityObject Identity

x Object identifier (OID) assigned to object when it is

created that is:

System-generated.

Unique to that object.

Invariant.

Independent of the values of its attributes (that is,

its state). Invisible to the user.


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F_NAME s

M_NAME s

L_NAME s

NAME

DEFINING THREE ABSTRACT DATA TYPE

BLDG.NO i

STREET s

CITY s

STATE s

PIN i

ADDRESS

DAY i

MONTH i

YEAR i

DOB



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NAME

ADDRESS

DOB

SEXAGE

EMPLOYEE

OBJECT REPRESENTATION FOR INSTANCES OF THE

CLASS EMPLOYEE WITH ADTS

NAME

ADDRESS

DOB

SEXAGE

Data Types


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F_NAME Sameer

M_NAME A.

L_NAME Sathe

NAME OID X 201

BLDG.NO 112

STREET N.L.Street

CITY Mumbai

STATE MAHA.

PIN 400018

ADDRESS OID X 202

DAY 23

MONTH 11

YEAR 1970

DOB OID X 203

NAME X 201

ADDRESS X 202

DOB X 203SEX M

AGE 30

EMPLOYEE OID X 20

OBJECT SCHEMA: GRAPHICAL REPRESENTATIONOBJECT SCHEMA: GRAPHICAL REPRESENTATION


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Object Identity Object Equalityx 2 objects are identical if they have the same OID

(o1 == 02)

x 2 objects are equal if they have the same value

(o1 = 02)

(o1 == 02) (o1 = 02)(o1 = 02) (o1 == 02)NON !


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Advantages of OIDs

x They are efficient.

x They are fast.

x They cannot be modified by the user.

x They are independent of content.

Value + OID = object


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INHERITANCE

I h i


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Inheritance


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Inheritance

CREATE TABLE contacts (contact person_typ,

contact_date DATE );

INSERT INTO contacts

VALUES (person_typ (12, 'Hemant Agashe', '99765432414'),

'24 Jun 2003' );

1 row created.


VALUES (student_typ(51, 'Sameer Bhende', '9967452317', 12,

'HISTORY'),'24 Jun 2003' );

1 row created.


VALUES (part_time_student_typ(52, 'Uday Chitale',

'9978561234', 14,'PHYSICS', 20), '24 Jun 2003' );

1 row created.


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Inheritance

SELECT TREAT(contact AS student_typ).major FROMcontacts;

TREAT(CONTACTASSTUDENT_TYP).MA

------------------------------

HISTORY

PHYSICS


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Inheritance

SQL> SELECT TREAT(contact AS student_typ).major ,TREAT(contact AS person_typ).name FROM contacts;

TREAT(CONTACTASSTUDENT_TYP).MATREAT(CONTACTASPERSON_TYP).NAME

------------------------------ ------------------------------

Hemant Agashe

HISTORY Sameer Bhende

PHYSICS Uday Chitale


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Database Design For ORDBMS

x Database designer can get an opportunity to use richvariety of data types for ORDBMS.

x Creating Collection Data types:

A varray is an ordered collection of elements.

A nestedtable can have any number of elements.


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The Nested Relational Data Model

x Not in 1NF

x Example:

dept = (dno, manager, employees, projects, locations)

employees = (ename, dependents)

projects = (pname, ploc)

locations = (dloc)

dependents = (dname, age)


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Email: sushiltry@yahoo co in Mob: 9967770658
mailto:[email protected]:[email protected]

Object Database system

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